Dependence of adhesion properties of SMR L based adhesive on molecular weight of rubber

Abstract

The viscosity, loop tack, peel and shear strength of five different molecular weights of standard Malaysian rubber based pressure sensitive adhesive were studied. Coumarone–indene resin and toluene were used as the tackifier and solvent respectively throughout the experiment. The adhesive was coated on polyethylene terephthalate substrate at a coating thickness of 30, 60, 90 and 120 μm using a Sheen hand coater. Viscosity of the adhesive was determined by a Haake rotary viscometer whereas loop tack, shear and peel strength was measured by a Llyod adhesion tester. Results show that viscosity of adhesive increases with increasing molecular weight of rubber. However, loop tack, shear and peel strength exhibit maximum value at a molecular weight of 8·5 × 104 where maximum wettability of adhesive on the substrate occurs. The adhesion property increases with coating thickness at this optimum molecular weight of rubber.